The present invention generally relates to standard primary batteries and, more particularly, to a primary battery cell with an integrated voltage regulator and a method for providing a standard size primary battery cell having a high energy density.
Commercially widely available standard primary (non-rechargeable) batteries include, for example, standard size alkaline or carbon-zinc batteries, such as D, C, AA, or AAA single-cell batteries, which have typically a standard output voltage of 1.5 V (volt) or lead-acid batteries that typically have a standard output voltage of 2.0 V. Most currently existing equipment used by consumers, often on a regular basis, utilizes these inexpensive standard primary batteries in single or multiple to get the correct voltage for the equipment. Standard primary batteries are often used by consumers in portable electronic devices, such as electronic calculators, electronic door locks, fire detectors, flashlights, radios, electronic toys, tape recorders, compact disc players, cameras, cellular phones, pagers, small kitchen appliances, and other cordless consumer products. As electronic devices become faster and more complex, the devices may require more power for operation and, therefore, typical standard primary batteries may need to be replaced more often. When a standard primary battery is not providing the needed current anymore it is typically thrown away. Therefore, a growing demand exits for longer lasting standard primary batteries. In addition, in areas where it is difficult to replace or service, consumers would often like to use higher cost but longer lasting technologies, for example, lithium-ion technology instead of the inexpensive standard primary batteries.
Consequently, it would be advantageous for the consumers to exchange standard primary batteries with higher energy density batteries, such as lithium-ion battery cells. Unfortunately this is currently not possible since the output voltage of such higher energy density battery cells is, for example with about 3.0 to 3.9 V, typically higher than the output voltage of about 1.5 V of a standard primary battery. Also future development of higher energy density battery cells could lead to even higher output voltages. To take advantage of modern technologies, such as the lithium-ion technology, equipment could be redesigned to use higher energy density battery cells, but this may not always be convenient, cost effective or even possible with existing equipment.
Various prior art, self-contained, portable energy storage devices exist that address these current market demands. For example, U.S. Pat. No. 6,654,228 utilizes a step-down voltage converter in a primary alkaline battery. The provision of a step-down voltage converter in a primary alkaline battery results in a substantially constant discharge voltage throughout the useful life of the battery and, therefore, the effective lifetime or the alkaline battery may be extended.
In another example, U.S. Pat. No. 6,232,749 describes a battery pack that includes a DC-DC (direct current) converter operatively coupled to a group of at least two primary cells. The DC-DC converter converts the voltage to a regulated nominal voltage that is lower than the rated voltage of the group of primary cells. By regulating the battery voltage down to a constant voltage, the cells can discharge down to a minimum voltage level per cell enabling additional energy transfer from the group of cells. While prolonging the lifetime of the battery pack, the described battery pack could not replace standard size primary batteries due to the form factor, the physical size and shape of the space receiving the standard size primary battery, in existing equipment.
As can be seen, there is a need for a standard size primary battery that has a longer effective lifespan than currently commercially available standard size primary batteries. Furthermore, there is a need to utilize high energy density technologies, such as the lithium-ion technology, for standard applications that meet the form factor of existing devices.